Alternating-current circuit breaker



June 24, 1930.

H. MCBRIDE 1,767,855

ALTERNATING CURRENT CIRCUIT BREAKER Filed Aug. 4, 1924 14,11 1iCBrid alto: nu

Patented 'June 24, 1930 PATENT OFFICE HENRY FLOYD MCBRIDE, OF SILAO, MEXICO ALTERNATING-CUBRENT CIRCUIT BREAKER Application filed August 4, 1924. Serial No. 729,964.

This invention relates to new and useful improvements in alternating current circuit breakers.

The primary object of this invention is to provide a circuit breaker which will operate upon the short circuiting or overloading of an alternating current line.

.A further object of the invention is to provide mechanical means for holding a switch in its circuit closing position and electrical means, rendered active upon the short circuiting or overloading of a line, for operating the mechanical means to release the switch.

A still further object of the invention is to provide a variable ratio current, transformer in connection with a thermo-electric expansion element for releasing mechanical means employed for holding a switch mechanism in its circuit closing position.

Another object of the invention is to pro vide means for multiplying the variations in an expansible element for causing such variations to release mechanical means employed for holding a switch in its circuit closin position.

A f urther object of the invention is to provide adjustable means for rendering the aforementioned thermo-electric expansion element active only upon the short circuiting or overloading of a line.

Other objects and advantages of the invention will be apparent during the course of the following description.

In the accompanying drawing formin a part of this specification and in which like numerals are employed to designate like parts throughout the same,

Figure 1 is a front elevational view of the cirguit breaker embodying this invention,

Figure 2 is a side elevational View of the circuit breaker illustrated in Fig. 1.

In the drawing, wherein for the purpose 4 of illustration is shown a preferred embodiment of this invention, the numeral 5 designates a base formed of any suitable insulating material, such as slate, porcelain, bakelite, etc. Suitably secured to the upper portion of this base 5 are a pair of spaced horseshoe magnets 6 which are each provided with a pair of U-shaped brackets 7 which are bolted to the outer faces of the magnets. These U-shaped brackets 7 are provided with elongated slots 8 which are formed in the portions of the brackets extending beyond the ends of the magnets. Adjustably connected to the projecting portions of these brackets, by means of the slots 8 and bolts 9, are the armatures 10, the adjustability of the said armatures being employed for permitting them to be moved toward and away from the ends of the horseshoe magnets 6 for the purpose of varying the reluctance of their magnetic circuits.

Suitably secured to the base 5 is a supporting block 11 which is employed for carrying the metallic tubes 12 which extend perpendicularly from the said block 11 and terminate in proximity to the bases of the horseshoe magnets 6. These tubes 12 are employed for carrying the thermo-electric expansion elements 13 which extend axially through the said tubes and are connected at their opposite ends to the bolts 14 and 15, the bolts 14 being provided with take-up nuts 16 while the bolts 15 are provided with nuts 17. It will be noticed that the bolts 1 1 and nuts 16 are insulated from the metallic tubes 12' by means of the washers 18.

Spring elements '19 are positioned between I the lower ends of the tubes 12 and the nuts 17, carried by the bolts 15, for the purpose of forcing downwardly upon these last mentioned bolts when the elements 13 expand axially thereby retaining the said elements 13 stretched to their full lengths at all times. The block 11 is provided with a pair of laterally projecting ears 20 which are employed for pivotally carrying the rod 21 to which is rigidly secured an overbalanced latch element 22 having the hooked end 23 which is positioned upon the lighter side of the pivot rod 21. Extending upwardly from this latch member 22 is an arm 24 having a knob 25 at its upper end by means of which the latch member may be operated manually. The overwcighted end 22 of the latch member 22 is provided with a perpendicularly extending post 26 which has its lower end operatively associated with the longer end 27 of: the mechanical multiplying levers 28 which are pivotally connected to the supporting bloc 11 by means of the bosses 29, the shorter ends 30 of the multiplying levers 28 being positioned in engagement with the lower ends of the bolts 15 carried by the thermo-expansion elements 13.

A suitable three pole, single throw, knife blade switch 31 is illustrated as being suitably mounted upon the base 5 and has its three stationary contacts 32 suitably arranged in spaced relation to each other below the supporting block 11. The movable contacts 33 are pivotally carried by the rod 3% which is supported by brackets 35. The rod 34 also carries the arms 36 which are operatively connected to the movable contacts or blades 33 by means of the pins 37 and slots 38. These arms 36 are provided with a handle portion 39 which is carried by the cross piece 10 that connects the arms 36 at their free ends. Suitably secured to the handle portion 39 is a hooked arm 41 which is adapted to be engaged by the hooked end 23 of the latch member 22 when the switch 31 is positioned in its full line position as illustrated in Fig. 2, or in other words, when the movable contact blades 33 are in electric connection with the stationary contacts 32. It will be understood that the weighted end 22 of this latch member 22 will retain the hooked end 23 in engagement with the hooked arm 41 of the switch 31 for retaining the latter in its circuit closing position.

Suitably mounted upon the horseshoe magnets 6 are the transformer coils 4:2. The lead wires 13 of the primary coils are connected to the binding posts 14:, while the second leads 4.5 of the primary coils extend through openings 46 in the base 5 for connection at their opposite ends 45* to the binding posts 17 of the outer stationary contacts 32. The leads 48 from the secondary coils are directly connected to the bolts 14: associated with the thermo-expansion elements 13 which are connected at their lower ends to the supporting block 11 and the metallic tubes 12 for arranging these elements 13 in series with the secondary coils of the transformers 42. The remaining two leads 49 of the secondary coils are oined and provided with a lead 50, common to both, which extends through opening in base 5 for being connected to supporting block 11.

It will now be seen that an alternating current circuit breaker has been provided which includes a specially designed variable ratio current transformer, the variable ratio of which is obtained by adjusting the armatures 10 toward and away from the ends of the horseshoe magnets 6 for varying the reluctance of these magnetic circuits. The magnetic circuits of these current transformers are so designed as to saturate on short circuits, or extremely heavy loads, which feature limits the maximum value of the current in the secondary circuits and thus affords protection under such conditions to the expansion elements 13 connected in series with the secondary coils. The expansion elements 13 may consist of straight lengths of nichrome, or other similar alloy, resistor wires while the metallic tubes 12 may be formed of: material which has a temperature co-efiicient of expansion equal to or closely approximating that of the resistor wires 13, thus automatically compensating for atmospheric temperature changes.

It will be noted that when the thermoexpansion elements 13 increase in length, due to axial expansion, the bolts 15 will force downwardly upon the shorter ends 30 of the multiplying levers 28 for causing the longer ends 27 to force upwardly upon the post 26 for pivoting the latch element 22 whereupon the hooked end 23 of this latch element will be moved out of engagement with the hooked arm 41 of the switch 31 for permitting the spring 51 to throw the said switch into its opened position. It will be noted that the difference in length of the arms 27 and 30 of the multiplying levers 28 will cause slight variations in length of the elements 13 to cause suflicient movement of the post 26 and latch member 22 for releasing the switch 31.

It is now believed that the construction and operation of this circuit breaking apparatus will be clearly understood from the above detail description and that no further explanation is deemed necessary. It is to be understood that the form of this invention herewith shown and described is to be taken as a preferred example of the same, and that various changes in the shape, size, and arrangement of parts may be resorted to without departing from the spirit of the invention or the scope of the subjoined claim.

Having thus described the invention, I claim In a switch of the type described, and comprising a series of thermally expansive elements, a series of contact terminals, a

normally open switch and a weighted tri lever to hold said switch in closed position, the combination therewith of means for unlocking said switch by the release of said lever, said means comprising a pair of levers mounted on separate ivots and having arms of unequal length the shorter arms being in operative relation to the thermal elements, and the longer arms in operative relation to the weighted trip lever whereby the expansion of the thermal elements is multiplied to effectively 0 erate the trip lever under small degrees of expansion.

In testimony whereof I have afiixed my signature.

HENRY FLOYD MCBRIDE. 

